A stirrer is the term representing an instrument for stirring and mixing liquid and liquid, liquid and solid, or powder. According to a kind of stirring, the stirrer may be classified into a tank type stirrer and a flowing type stirrer. Currently, most of stirrers which have been widely used are the tank type stirrer. The tank type stirrer has a structure in which a device for stirring an object is mounted in a tank, and may be classified into various kinds such as a propeller type stirrer, an oar type stirrer, a turbine type stirrer, and a spiral shaft type stirrer according to a shape of a stirring blade.
The propeller type stirrer is used for stirring liquid having a low viscosity or liquid containing solid particles. The oar type stirrer has the simplest structure for stirring objects having a low viscosity. The turbine type stirrer utilizes a centrifugal force and is very efficient. The spiral shaft type stirrer is employed for stirring objects having a high viscosity. A movement of liquid in the stirrer has a large influence on a stirring effect, and the movement of liquid is variously influenced by a shape of a container, a shape and a position of the stirrer, and an existence/nonexistence of a baffle (baffle plate). In general, the stirrer including the baffle provides a good stirring effect. In a chemical industry field, the stirrer is mainly for a chemical reaction, is used for combining, dissolving, cleaning, dispersing, and adsorbing substances, and is used for transferring heat. A household washing machine is one kind of the stirrer. Additionally, a movable stirrer in which fluid is pumped by a pump and is then stirred is employed, and this movable stirrer is suitable for continuously mixing liquids having a low viscosity.
In general, a flow formed by the stirrer is strongly formed in the rotational direction of the stirrer, and thus the strength of the flow in the upward/downward direction of the stirrer container is weaker than that of the flow in the rotational direction. Due to the above, a degree of mixing in the upward/downward direction of the stirring container is low, and a stirrer in which a plate-shaped baffle is installed has been proposed in order to improve the above problem. However, in the stirrer in which the plate-shaped baffle is installed, a region in which a flow velocity is rapidly reduced is formed around the baffle, foreign substances are generated around the baffle and an internal structure or an inner surface of the container, and shapes of particles are irregular due to a rapid change of the internal flow in the stirrer.